1. Field of the Invention
The present invention relates to a mobile telecommunications system and a mobile telecommunications control method using a radio mobile station such as a cell phone and in particular to handover control for switching a radio base station to communicate with the radio mobile station.
2. Description of the Related Art
In a related art mobile telecommunications system, in case handover control is made while a radio mobile station is communicating with a radio base station to switch over to communications with another radio base station, a downlink spread code to identify the radio wave direction (sector) of a radio base station called the scramble code in the report information from the radio base station engaged in communications is given as peripheral radio base station information to the radio mobile station. The radio mobile station measures the downlink communications quality of this spread code to determine the radio base station as a handover destination. On top of this related art method, handover control using position information obtained from the GPS has been disclosed (refer to the Japanese Patent Laid-Open No. 2002-199428, Page 5, FIG. 2).
In the related art mobile telecommunications system, in case a radio mobile station performs handover control, a downlink spread code (scramble code) in the information reported from the radio base station engaged in communications is given to the radio mobile station. The radio mobile station performs handover control based on the downlink communications quality corresponding to the spread code. However in case the radio mobile station travels at a high-speed on a highway or Shinkan-sen train, handover control which is based on the downlink communications quality causes the communications quality of an adjacent radio base station to vary drastically, which increases the handover control count. Due to a high-speed travel of the radio mobile station, handover control using ordinary handover control parameters generates a time lag in the handover control timing thus blocking the control data for radio telecommunications and releasing the ongoing call.